1. Technical Field
The present invention relates to a radiation image capture device, and particularly relates to a radiation image capture device in which a radiation detection panel and a signal processing board are connected by a flexible printed circuit (FPC).
2. Related Art
In recent years, radiation image detectors such as flat panel detectors (FPD) and the like have been realized. In an FPD, a radiation-sensitive layer is disposed on a thin film transistor (TFT) active matrix substrate, and the FPD is capable of converting radiation directly to digital data. A radiation image capture device that uses this radiation detector has the advantage, over prior art radiation image capture devices that use X-ray films, imaging plates and the like, that images may be checked immediately. This device also has the advantage of being able to perform radioscopic imaging (video imaging) in which radiation images are successively imaged.
Diverse types of this kind of radiation detector have been proposed. For example, a radiation detector that employs an indirect conversion system converts radiation to light using a scintillator, converts the converted light to electronic charges with sensor portions such as photodiodes or the like, and accumulates these charges. The accumulated charges are information about a radiation image captured by X-ray imaging. CsI:Tl, GOS (Gd2O2S:Tb) or the like is used for the scintillator. A radiation image capture device reads out the charges accumulated in the radiation detector in the form of analog signals, amplifies the analog signals with amplifiers, and then converts the analog signals to digital data with an analog-digital (A/D) converter.
Japanese Patent Application Laid-Open (JP-A) No. 2009-257914 discloses a cassette-type radiation image detector that may prevent occurrences of failures. In this cassette-type radiation image detector, an image detection unit provided with a sensor panel, a base and a flexible cable is incorporated inside a housing. The sensor panel includes an optoelectronic conversion unit and a scintillator that converts incident radiation to light. The base is disposed to oppose the sensor panel, and is provided with a circuit relating to the optoelectronic conversion unit. The flexible cable electrically connects the optoelectronic conversion unit with the circuit, and has a chip on film (COF) structure, at which an integrated circuit component or the like is mounted, or suchlike. A side face portion of the housing that opposes the flexible cable is formed in a curved shape to match a curved form of the flexible cable. In order to release heat produced in association with operations of the integrated circuit component and the like, the flexible cable makes area contact with an inner wall portion of the curved shape of the side face portion of the housing. A housing main body of the housing is formed using carbon fibers with high thermal conductivity.
In the cassette-type radiation image detector with this structure, because the side face portion of the housing is formed in a curved shape with substantially the same curvature as the curvature with which the flexible cable is bent, even if the flexible cable vibrates, vibrations are impeded by the curved shape of the side face portion, and the flexible cable does not detach from the side face portion. Therefore, rubbing between the side face portion of the housing and the flexible cable may be prevented, and failures such as severing of wires in the flexible cable and the like due to the rubbing may be prevented.
The housing main body of the housing of the cassette-type radiation image detector disclosed in JP-A No. 2009-257914 is conductive, and the housing main body functions as an electromagnetic shield. Thus, electromagnetic noise coming from outside the cassette-type radiation image detector may be prevented. However, only very narrow gaps with dimensions of a few millimeters can be reserved between the inner wall portions of the housing main body and circuits provided at the sensor panel, the base and the like. If, in accordance with adjustments of position and posture of an imaging subject (a patient) during and before X-ray imaging, there is a touch, an impact or the like between the imaging subject and the cassette-type radiation image detector, a portion of the sensor panel or a portion of the circuits touches against the housing main body.
JP-A No. 2010-264250 discloses an X-ray imaging device that detects when irradiations of radiation start and stop and the like, and that does not require control for synchronization with radiation generation timings. In this X-ray imaging device, if a portion of a sensor panel or a portion of a circuit touches against a housing main body when there is electromagnetic noise on the housing main body, the electromagnetic noise causes changes in analog signals in the sensor panel, circuit and the like. These changes in the analog signals lead to misdetections of captured X-ray image data.
In the cassette-type radiation image detector disclosed in JP-A No. 2009-257914, in order to release heat produced in association with operations of the integrated circuit components and the like while preventing rubbing, the flexible cable makes area contact with the inner wall portion of the side face portion of the housing main body. The same as described above, when there is electromagnetic noise on the housing main body or the like, the electromagnetic noise causes changes in analog signals being propagated in the wiring of the flexible cable, leading to misdetections of captured X-ray image data.
In order to avoid misdetections of captured X-ray image data due to such electromagnetic noise, it is effective to fabricate the housing main body of a cassette-type radiation imaging device of an insulator and keep the flexible cable separated from the inner wall portion of the side face portion of the housing main body. However, although fabricating the housing main body using an insulator is effective as a measure against electromagnetic noise, when a touch, impact or the like is applied as mentioned above, the flexible cable touches or rubs against the inner wall portion of the housing main body, there is electrostatic charging of wiring in the flexible cable, and counter (compensation) charges are produced.
A method of utilizing processing software that distinguishes X-rays from noise on the basis of changes of charge amounts over time is given as a method for preventing misdetections of captured X-ray image data. When judgments are made by such processing software, the likelihood of a misdetection of X-rays when there is noise may be reduced. However, when the duration of processing by processing software is increased, there is at a reduction in workflow, an increase in losses of X-ray data during X-ray irradiation, and suchlike. Accordingly, technologies that suppress the actual production of noise are in demand.
Similarly, in an X-ray imaging device that requires control for synchronization with radiation generation timings, if electrostatic charging occurs at wiring in a flexible cable, there are changes in the analog signals during a read-out of captured X-ray image data. These changes in the analog signals appear as noise in captured X-ray images. This noise may be identified from patterns in captured X-ray images and may be corrected using processing software. However, when the duration of processing by processing software increases, time is required until display of a radiation image and the like, and there is a reduction in workflow.